To reduce animal stress and labor costs, it is desirable to vaccinate animals with as few doses as possible to achieve effectiveness. A combination vaccine against multiple pathogens that delivers an effective amount of antigen against each respective pathogen is desired. Practitioners and producers can achieve a combination vaccine by mixing antigens against multiple respective pathogens just prior to vaccination. But, such preparation in the field can introduce admixing errors, and there is no certainty that the combinations of antigens are compatible with one another.
It is desirable to have a premixed combination vaccine against multiple pathogens available so that labor costs and potential dosing errors are reduced and an effective dose of antigen against each respective pathogen is reliably delivered to a subject.
To reduce manufacturing costs, it is desirable to streamline vaccine production. For example, checking the quality of a cell culture for the desired immunogenic material prior to harvest or prior to admixing multiple immunogenic compositions together can reduce variability and waste.
To gain regulatory approval for a therapeutic immunogenic composition, e.g., a vaccine, as well as for safety reasons, a means of monitoring the antigen quantity and stability of the composition is required. Historically, that method has been ELISA-based. ELISA requires the availability of a suitable antibody for the antigen to be measured. But, ELISA-based methods can face certain obstacles: (1) suitable antibodies are not always available; and (2) these methods are not always able to reliably quantify and precisely quantify (e.g. ±10% deviation) complex biotherapeutics. This latter obstacle is especially problematic when multiple antigens are present in a vaccine.
However, for a combination vaccine to become a commercial product, the reference stability of the combined antigens must be ascertainable in the combination. That is, the amount of each respective antigen must be determinable over time after they are combined to ensure that the desired amount of each respective antigen is present in each dose.
In some combination vaccines, the individual vaccine preparations may contain elements that interfere with the detection of the other vaccine components using standard techniques. For example, a combination vaccine may contain a first and a second antigen, wherein the second antigen formulation may include serum from animals which have been exposed to an organism containing the first antigen, or which have been vaccinated with an antigen identical to or antigenically similar to the first antigen. In this situation, the first antigen may have elicited production of competing antibodies specific to the first antigen; thus, the serum present in the second antigen formulation may contain antibodies to the first antigen and these antibodies may be present in the combination vaccine. As a result, the standard immunological means for monitoring the reference stability of the first antigen in a single-component vaccine (i.e., ELISA) would be unable to adequately ascertain the stability of the resulting combination vaccine. In the absence of a suitable ELISA assay, the antigen stability and the efficacy of the vaccine would be determined in a clinical study in the host animal. The clinical study would entail vaccination of a statistically relevant number of animals followed by challenge. Clinical studies are expensive to perform, including the cost of animals, need for suitable housing (biocontainment), and testing of clinical samples collected during the study. An alternative means suitable for monitoring large scale manufacturing and for reliably determining the final concentrations of respective antigens in a combination vaccine are needed.